The object of these studies will be to develop a method for prevention and treatment of pyelonephritis in subjects predisposed to kidney infection by gram negative bacteria resistant to antibiotics. The proposed experiments are based on the concept that kidney infection can be prevented by immobilizing the bacteria, counteracting their "O" antigens, and damaging the cytoplasmic membranes of L-forms or of the bacilli themselves with antibody. Since previous studies from this laboratory indicate that only 7S antibody reaches the kidney and urine in effective antimicrobial concentrations after vaccination, an attempt will be made to develop experimental methods for delivering 7S immobilizing antibody, "O" antibody, and cytoplasmic-membrane antibody to the urinary tract in concentrations that will prevent infection of the kidney. If these experiments succeed, it may then be possible by means of vaccines and antisera to provide the immunity against pyelonephritis that fails to occur during the lower urinary tract infections from which pyelonephritis develops.